Interleaving a bondwire between two bondwires coupled to a same terminal

ABSTRACT

An integrated circuit device package. A substrate includes a first terminal coupled to the substrate. First and second conductive traces are formed on the substrate and are electrically coupled to the first terminal wherein the first conductive trace is provided to electrically couple a first bondwire to the first terminal and the second conductive trace is provided to electrically couple the second bondwire to the first terminal.

FIELD OF THE INVENTION

The present invention relates generally to the field of integratedcircuit device packages, and more particularly, to connections betweenan integrated circuit die and terminal(s) on an integrated circuitdevice package.

BACKGROUND OF THE INVENTION

While integrated circuit devices continue to increase in complexity,keeping costs low and form factors small is still a focus for manyapplications. A key factor in determining the cost and space taken up bya particular integrated circuit device can be the package in which theintegrated circuit device is provided.

For integrated circuit devices such as microprocessor chipsets, forexample, that are particularly cost- and space-sensitive, a relativelysmall plastic package having a dense input/output terminal pattern maybe used. Ball grid array (BGA) packages, for example, are increasinglypopular because they are capable of providing a dense terminal array ina relatively small area at a relatively low cost.

"Terminals" as the term is used herein, refers to external, electricallyconductive features provided on a package for transferring signals toand from the integrated circuit die within the package. Types ofterminals include pins, solder balls, polymer balls coated with aconductive material, solder columns, land pads, etc. The type ofterminal depends on the type of package being used.

To transfer signals to and from an integrated circuit die within apackage, bondwires may be used to electrically connect bondpads on theintegrated circuit die to bondfingers or bondposts on a packagesubstrate. Individual traces and vias on the package substrateelectrically couple the bondfingers to the respective terminals thatprovide the input/output connections for the package.

The routing of electrical connections from bondpads on the integratedcircuit die to the package terminals presents several challenges forintegrated circuit package designers. In particular, there may be morebondpads on the integrated circuit die (or bondwires from the integratedcircuit die to the package substrate) than there are available terminalson the package. This circumstance may arise, for example, where multiplepower and/or ground connections to the integrated circuit die areprovided. Multiple power and/or ground connections are desirable in manycases to improve the quality and strength of the signals transmitted toand from an integrated circuit die.

One approach to addressing this issue is illustrated in FIG. 1. FIG. 1is a top view of a portion of a package substrate 10 having anintegrated circuit die 11 mounted thereon. The integrated circuit die 11includes a double bondpad 12 and two bondwires 13 extending from thebondpad 12 to a double bondfinger 14. The double bondfinger 14 iselectrically connected to a single conductive trace 15 extending to asingle via 16. The via 16 is electrically connected by a conductivetrace on another layer or surface of the substrate 10 to a single powerterminal 17 (shown in phantom). The power terminal 17 is coupled to anunderside of the package substrate 10. In this manner, the packagesubstrate 10 of FIG. 1 provides for multiple power connections to asingle power terminal 17 such that the number of bondpads on the die 11may be greater than the number of available terminals.

A disadvantage of this approach, however, is that while a groundconnection may be provided on either side of the double powerconnection, a ground bondwire or other ground connection cannot beprovided between the two power bondwires 13. Lack of a ground connectionbetween the two power bondwires 13 of FIG. 1 can cause the inductance ofthe combined power connection to be undesirably high. High inductancecan adversely affect device performance.

Further, different types of bondwires and/or integrated circuit devicepackages including substrates that are different than the substrate 10of FIG. 1 that have dense terminal layouts may present similar issues.

SUMMARY OF THE INVENTION

An integrated circuit device package includes a substrate including afirst terminal coupled to the substrate. First and second conductivetraces are formed on the substrate and electrically coupled to the firstterminal, wherein the first conductive trace is to couple a firstbondwire to the first terminal and the second conductive trace is tocouple a second bondwire to the first terminal.

Other features and advantages of the present invention will be apparentfrom the accompanying drawings and from the detailed description thatfollows below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings, in which likereferences indicate similar elements, and in which:

FIG. 1 is a partial top down view of a package substrate, semiconductordie and conductive traces of a prior integrated circuit device package.

FIG. 2 is a partial top down view of a package substrate, semiconductordie and arrangement of conductive traces of one embodiment.

FIG. 3 is a partial cross-sectional view of the package substrate,semiconductor die and conductive traces of FIG. 2 taken along the line3--3.

FIG. 4 is a partial cross-sectional view of the package substrate ofFIG. 2 taken along the line 4--4 showing the manner in which the firstand second conductive traces are electrically coupled to a singleterminal.

FIG. 5 is a flow diagram showing the package construction method of oneembodiment.

FIG. 6 is a flow diagram showing the package construction method of analternate embodiment.

DETAILED DESCRIPTION

An integrated circuit device package that enables an increase in thenumber of bondwires without a corresponding increase in the number ofterminals, and method for constructing the same are described. Althoughthe embodiments described below refer to a ball grid array (BGA) packagefor purposes of illustration, other types of integrated circuit devicepackages such as column grid arrays, for example, may also be used inaccordance with various embodiments.

An intended advantage of one or more embodiments is to electricallycouple two or more bondwires to a single terminal while enabling abondwire that is electrically coupled to another terminal to beinterleaved between the two bondwires. In this manner, integratedcircuit package designers are provided with more flexibility for routingconnections from an integrated circuit die to package terminals. Morespecifically, an intended advantage of one or more embodiments is toenable a ground bondwire that is electrically coupled to a groundterminal to be interleaved between two power bondwires that areelectrically coupled to a single power terminal. Other advantages willbe appreciated from the description that follows.

FIG. 2 shows a partial top down view of a package substrate 20 on whichan integrated circuit die 21 is mounted. The package substrate 20 ispart of a ball grid array (BGA) package for this example, however, othersubstrates that are used with different types of packages may also beused in accordance with the invention.

The package substrate 20 of one embodiment is formed of an insulatormaterial such as an epoxy-glass resin as shown in more detail in FIGS. 3and 4. For other embodiments, the package substrate may be formed ofanother substrate material.

The integrated circuit die 21 coupled to the package substrate 20includes bondpads 27. The bondpads 27 are contact areas on theintegrated circuit die 21 through which signals are transferred to andfrom the integrated circuit die 21 during operation.

Each of the bondpads 27 is electrically connected to a correspondingbondfinger 23, and thus, to a corresponding conductive trace 22, by abondwire 28. The bondwires 28 may be formed of gold or another lowresistance, electrically conductive material. The process ofelectrically connecting a bondpad 27 to a corresponding bondfinger 23with a bondwire 28 is often referred to as "bonding out" the bondpad tothe bondfinger (or to the corresponding conductive trace).

For other embodiments, some of the bondpads, in particular the groundbondpads, may be bonded out to a conductive area other than abondfinger. This conductive area may be a ground paddle, for example,that extends from beneath the integrated circuit die. In this case, thebondpads are "downbonded" to the ground paddle. Other types ofconductive structures to which wires can be bonded can also be used foralternative embodiments.

The package substrate 20 includes conductive traces 22 on a firstsurface of the package substrate 20, each of which has a bondfinger 23at one end and includes a conductive via 24 that may be at the oppositeend of the conductive trace 22. The bondfingers 23 of this embodimentare slightly wider areas of the conductive traces 22 that provide forbonding out of the integrated circuit die 21 to the conductive traces22. It will be appreciated that conductive traces of other embodimentsmay not include bondfingers at one end, may extend beyond the vias ormay be configured in a different manner than shown in FIG. 2.

Each of the vias 24 electrically couples the corresponding conductivetrace 22 to a terminal 25 (shown in phantom) on an external surface ofthe package substrate 20. The vias 24 extend through the packagesubstrate 20 and are each electrically coupled directly to one of theterminals 25 or indirectly by an intermediate conductive trace 26 (alsoshown in phantom in FIG. 2) on another surface of the package substrate20. The conductive traces 26 are referred to herein as intermediateconductive traces. Some of the intermediate conductive traces 26 mayextend beneath the integrated circuit die 21 to reach terminals that arelocated beneath the integrated circuit die (not shown). Also, for otherembodiments, the layout of the vias 24 may be different than thearrangement shown in FIG. 2. The manner in which the vias 24 and theconductive traces 26 are coupled to the terminals 25 is shown in moredetail in FIGS. 3 and 4.

The conductive traces 22 and bondfingers 23 of one embodiment are formedusing conventional lithographic techniques. For example, the conductivetraces 22 and bondfingers 23 may be formed of copper that is depositedon the substrate, patterned, etched and plated with gold and/or nickel.The conductive traces 22 and bondfingers 23 may be patterned and formedsimultaneously such that the bondfingers 23 are an integral part of theconductive traces 22. Alternatively, the bondfingers 23 and conductivetraces 22 may be formed separately, but in a manner such thatcorresponding conductive traces 22 and bondfingers 23 are electricallycontinuous. Also, for another embodiment, the conductive traces 22 andbondfingers 23 may be formed of different materials using a differentprocess.

Now with reference to specific elements described generally above, thebondpads 27 include bondpads 27a-d. The bondpads 27a and 27b for thisexample are both power bondpads, i.e. bondpads to which a supply voltageis to be applied during operation. The bondpad 27c (located between thebondpads 27a and 27b) and the bondpad 27d (located adjacent to thebondpad 27a) are ground bondpads that each receive a ground signalduring operation.

Bondwires 28a-d electrically connect bondpads 27a-d to bondfingers23a-d, respectively, and thus, to conductive traces 22a-d. The bondwires28a and 28b are referred to as power bondwires as they are each coupledto transfer a supply voltage to the power bondpads as described below.Similarly, the bondwire 28c (located between the bondwires 28a and 28b)and the bondwire 28d (located adjacent to the bondwire 28a), arereferred to as ground bondwires as they are coupled to transfer a groundsupply to the ground bondpads 28c and 28d.

The bondfinger 23c corresponding to the bondwire 28c is located betweenbondfingers 23a and 23b, while the bondfinger 23d is located adjacent tothe bondfinger 23a. Similarly, the conductive trace 22c corresponding tothe bondwire 28c is located between conductive traces 22a and 22b, whilethe conductive trace 22d is located adjacent to the conductive trace22a.

The conductive trace 22a is electrically coupled to a power terminal25ab by the conductive via 24a and intermediate conductive trace 26a.The conductive trace 22b is also electrically coupled to the powerterminal 25ab by the via 24b and intermediate conductive trace 26b.Similarly the conductive traces 22c and 22d are electrically coupled tothe ground terminals 25c and 25d, respectively by vias 24c and 24d andconductive traces 26c and 26d, respectively.

The manner in which the conductive traces 22a through 22c are coupled toterminals 25 on the package substrate 20 is described in more detailwith reference to FIGS. 3 and 4.

FIG. 3 shows a cross-section of a ball grid array package 30 includingthe package substrate 20 and integrated circuit die 21 of FIG. 2 takenat the line 3--3. For one embodiment, the die 21 is attached to thepackage substrate 20 by die attach material 31. The terminals 25 areprovided on a bottom surface of the package substrate 20 to transfersignals to and from the integrated circuit die 21 when it is coupled toa printed circuit board in a system, for example. While the terminals 25of FIG. 3 are solder balls, other types of terminals such asconductor-coated polymer balls, solder columns, land pads or pins may beused for other embodiments. Further, the package substrate for otherembodiments may include multiple layers.

The bondwire 28c that electrically connects the bondpad 27c to thebondfinger 23c (FIG. 2) and thus, to the conductive trace 22c is shownin FIG. 3. Also, as shown in FIG. 3, the conductive trace 22c extendsacross a top surface of the package substrate 20 to the via 24c. The via24c electrically connects the conductive trace 22c to the intermediateconductive trace 26c that extends across a bottom surface of the packagesubstrate 20. (The intermediate conductive trace 26c is shown in phantomin FIG. 2). The intermediate conductive trace 26c electrically couplesthe via 24c to a conductive terminal pad 35c between the ground terminal25c and the package substrate 20. The ground terminal 25c is formed onand electrically coupled to the terminal pad 35c. In this manner, theconductive trace 22c is electrically coupled to the ground terminal 25c.

The ground terminal 25c as well as other ground terminals on the package30 receives a ground supply during operation from a circuit board orother apparatus to which the package 30 is connected. The ground supplyis then provided to the ground bondpad 27c of FIG. 2 by way of theconductive trace 22c and the bondwire 28c.

FIG. 3 also shows the via 24a above the power terminal 25ab. The via 24ais coupled to the conductive trace 22a. The manner in which theconductive traces 22a and 22b are electrically coupled to the powerterminal 25ab is now described with reference to FIG. 4.

The via 24b is coupled to the conductive trace 22b. The via 24b iselectrically coupled to the intermediate conductive trace 26b (shown inphantom in FIG. 2) that extends along a bottom surface of the packagesubstrate 20 to a conductive terminal pad 35ab. The conductive terminalpad 35ab is electrically coupled to the power terminal 25ab. In thismanner, the conductive trace 22b (FIG. 2) is electrically coupled to thepower terminal 25ab.

The conductive trace 22a (FIGS. 2 and 3) is also electrically coupled tothe power terminal 25ab by the via 24a that extends through the packagesubstrate 20 to the conductive terminal pad 35ab.

In the manner described above, two power bondwires 28a and 28b areelectrically coupled through conductive traces 22a and 22b to a singlepower terminal 25ab while a ground bondwire 28c and conductive trace 22ccoupled to a ground terminal 25c are interleaved between the powerconnections. The power terminal 25ab is so called because, duringoperation, it receives a supply voltage through a circuit board or otherapparatus to which the package 30 is connected.

Referring back to FIG. 2, the embodiments described herein provide theadvantage that two bondwires can be electrically coupled to a singleterminal while allowing a third bondwire coupled to a different terminalto be interleaved between the first two bondwires. Specifically for oneembodiment, power bondwires 28a and 28b can be electrically coupled toone power terminal 25ab such that the number of power bondwires can beincreased without requiring an increase in the number of powerterminals. Further, the embodiment shown in FIG. 2 provides for a groundbondwire 28c coupled to a ground terminal to be interleaved between thetwo power bondwires 28a and 28b that are coupled to the single powerterminal 25ab.

Also, another ground bondwire 28d is provided adjacent to the powerbondwire 28a for one embodiment. In this manner, ground bondwires 28cand 28d are provided in close proximity to the power bondwires 28a and28b such that the loop formed by the power to ground circuit can berelatively small. The inductance of the power connections provided bythe power bondwires 28a and 28b is therefore reduced as compared to thedouble power connection of FIG. 1 that does not provide for a groundbondwire to be interleaved between the two power connections.

For another embodiment, a signal bondwire may be interleaved between twopower bondwires coupled to the same terminal in a similar manner.Further, any type of bondwire may be interleaved between any twobondwires coupled to a same terminal in accordance with variousembodiments. In this manner, it may be possible to reduce the number ofterminals provided on an integrated circuit device package withoutreducing the flexibility of the package or integrated circuit designerin routing connections or placing bondpads, respectively.

The integrated circuit device package construction method of oneembodiment is now described with reference to FIG. 5. The steps shown inFIG. 5 may be performed in a different order for different embodiments.

At step 51, first, second and third conductive traces are formed on apackage substrate with the third conductive trace being formed betweenthe first and second conductive traces. The conductive traces may beformed on the substrate using conventional lithographic methods, forexample. For an alternative embodiment, a third conductive area such asa ground plane is formed in place of the third conductive trace.

A power terminal and a ground terminal are each formed on the packagesubstrate at step 52. At step 53, the first and second conductive tracesare electrically coupled to the power terminal and at step 54, the thirdconductive terminal is electrically coupled to the ground terminal.

FIG. 6 is a flow diagram illustrating the package construction method ofanother embodiment. The steps provided below may be performed in anorder other than that shown in FIG. 6. At step 61, first, second, thirdand fourth conductive traces are formed. The third conductive trace isformed between the first and second conductive trace, and the fourthconductive trace is formed adjacent to one of the first or secondconductive traces. For an alternative embodiment, a conductive area isformed in place of the third conductive trace. The conductive area maynot necessarily extend between the first and second conductive traces,but provides for a bondwire connected to the conductive area to beinterleaved between the first and second conductive areas.

At step 62, a power terminal and two ground terminals are formed on thesubstrate. Other terminals may also be formed during this step. For oneembodiment, the package is a ball grid array and each of the power andground terminals is a solder ball or a polymer ball coated with aconductive material. Also, for one embodiment, the power and groundterminals are formed on a side of the substrate opposite the side onwhich the first through fourth conductive traces are formed.

At step 63, a first via is formed to electrically connect the firstconductive trace to the power terminal. A second via is formed at step64 to electrically connect the second conductive trace to the firstconductive trace and/or to the power terminal, and at step 65, a thirdvia is formed to electrically connect the third conductive trace to thefirst ground terminal. At step 66, the fourth conductive trace iselectrically coupled to the second ground terminal by a via or inanother manner. The first, second, third and fourth vias may be formedusing conventional methods. For example, the vias may be formed bydrilling or otherwise forming holes in the substrate and then fillingthe holes or plating the sidewalls of the holes with a conductivematerial.

At step 67, first, second and third bondpads on an integrated circuitdie are bonded out to the first, second and third conductive tracesrespectively. A fourth bondpad may also be bonded out the fourth trace.The third bondpad is between the first and second bondpads and thefourth bondpad is adjacent to one of the first or second bondpads. Thestep of bonding out the bondpads to corresponding traces includes a stepof connecting a bondwire from each bondpad to the correspondingconductive trace for one embodiment.

Where a third conductive area is formed instead of the third conductivetrace, the step of bonding out may include a step of downbonding thethird bondpad to the third conductive area with a third bondwire. Forthis embodiment, as for the embodiment described above, the thirdbondwire is between the first and second bondwires and the third bondpadis between the first and second bondpads.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however beappreciated that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

What is claimed is:
 1. An integrated circuit device package comprising:asubstrate including a first surface, a second surface, and a firstterminal coupled to the second surface; and first and second conductivetraces formed on the first surface of the substrate, the first andsecond conductive traces both electrically coupled to the firstterminal, the first conductive trace having a first bondfinger, thesecond conductive trace having a second bondfinger.
 2. The integratedcircuit device package of claim 1 further including:a second terminalcoupled to the second surface; and a third conductive trace formed onthe first surface of the substrate and electrically coupled to thesecond terminal, the third conductive trace having a third bondfingerlocated between the first and second bondfingers.
 3. The integratedcircuit device of claim 2 wherein the first terminal is a power terminaland the second terminal is a first ground terminal.
 4. The integratedcircuit device package of claim 3 further including an integratedcircuit die including first, second and third bondpads, the first andsecond bondpads being electrically coupled to the first and secondconductive traces by the first and second bondwires, the third bondpadbeing adjacent to and between the first and second bondpads and beingelectrically coupled to the third conductive trace by a third bondwire.5. The integrated circuit device package of claim 1 wherein the firstand second conductive traces are electrically coupled to each other by avia.
 6. The integrated circuit device package of claim 3 wherein thefirst and second conductive traces are electrically coupled to the powerterminal by a first via and wherein the third conductive trace iselectrically coupled to the first ground terminal by a second via. 7.The integrated circuit device package of claim 3 further including afourth conductive trace formed on the first surface of the substrateadjacent to one of the first or second conductive traces, the fourthconductive trace being electrically coupled to a second ground terminalcoupled to the second surface of the substrate.
 8. A packaged integratedcircuit device comprising:a substrate including a first surface, asecond surface, and a first terminal coupled to the second surface;first and second conductive traces formed on the first surface of thesubstrate; an integrated circuit die attached to the substrate, theintegrated circuit die having a first bondpad and a second bondpad;first and second bondwires electrically coupling the first and secondbondpads, respectively, on the integrated circuit die to the first andsecond conductive traces respectively, the first and second conductivetraces being electrically coupled to the first terminal; and a thirdbondwire electrically coupling a third bondpad adjacent to and betweenthe first and second bondpads to a second terminal coupled to the secondsurface of the substrate, the third bondwire being between the first andsecond bondwires; wherein the first terminal is a power terminal and thesecond terminal is a ground terminal.
 9. The packaged integrated circuitdevice of claim 8 further including:a fourth bondwire adjacent to one ofthe first or second bondwires, the fourth bondwire electrically couplinga fourth bondpad on the integrated circuit die to a third terminalcoupled to the second surface of the substrate, wherein the thirdterminal is a grounded terminal.
 10. The integrated circuit devicepackage of claim 8 further including:a first via electrically couplingthe first conductive trace to the first terminal, and a second viaelectrically coupling the second conductive trace to the first terminal.11. An integrated circuit device comprising:a substrate having a firstsurface and a second surface; first and second terminals coupled to thesecond surface; first and second conductive traces formed on the firstsurface of the substrate and electrically coupled to the first terminal;and an integrated circuit die including first, and second and thirdbondpads, the third bondpad being located adjacent to and between thefirst and second bondpads, the first and second bondpads beingelectrically coupled to the first terminal by the first and secondconductive traces, respectively, the third bondpad being electricallycoupled to the second terminal; wherein the first terminal is a powerterminal and the second terminal is a ground terminal.
 12. Theintegrated circuit device of claim 11 wherein the integrated circuit diefurther includes a fourth bondpad adjacent to one of the first or secondbondpads, the fourth bondpad being electrically coupled to a thirdterminal coupled to the second surface of the substrate.
 13. Theintegrated circuit device of claim 12 wherein the third terminal is aground terminal.
 14. A ball grid array package comprising:a substratehaving an inner layer and two outer layers; a power terminal and a firstground terminal formed on one of the two outer layers of the substrate;first and second conductive traces formed on the other of the two outerlayers of the substrate and electrically coupled to the power terminal,the first conductive trace further being electrically coupled to a firstbondwire, the second conductive trace further being electrically coupledto a second bondwire; and a third conductive trace formed on one of theinner and outer layers of the substrate, the third conductive tracebeing electrically coupled to the first ground terminal and to a thirdbondwire between the first and second bondwires.
 15. The ball grid arraypackage of claim 14 wherein the first and second conductive traces arecoupled to each other by a via.
 16. The ball grid array package of claim14 further including an integrated circuit die, the integrated circuitdie including first, second and third bondpads, the first, second andthird bondwires being electrically coupled to the first, second andthird bondpads, respectively, the third bondpad being adjacent to andbetween the first and second bondpads.
 17. The ball grid array packageof claim 14 wherein the first and second conductive traces areelectrically coupled to the power terminal by at least one via.
 18. Theball grid array package of claim 14 wherein the third conductive traceis electrically coupled to the first ground terminal by a via.
 19. Theball grid array package of claim 14 further including a fourthconductive trace formed on the substrate adjacent to one of the first orsecond grounded terminal coupled to one of the inner and outer layers ofthe substrate.